What is the summer solstice?

Also known as 'midsummer', when a planet's rotational axis tilts most towards the star that it orbits - or in earths' case, when it tilts to a maximum of 23.44° towards the sun - this is when the 'summer solstice' occurs.

This day has the longest period of daylight and happens twice each year: in the Northern Hemisphere in June and in the Southern Hemisphere between 20th and 23rd December (conversely when the Northern Hemisphere's 'winter solstice' - the shortest day - occurs).

During the summer solstice of the Northern Hemisphere, countries far north like Norway can even experience 24-hours continuous daylight - a phenomenon which lasts for a days or even months (depending on proximity to the North Pole).

When is the summer solstice?

The summer solstice falls between 20th and 22nd June each year in the Northern Hemisphere - commonly on 21st June - and is the longest day of the year.

This year, it falls on Friday, June 21.

The solstice itself is the exact time the sun shines over the Tropic of Cancer, which this year will be at 4.54pm in the UK.

In the northern hemisphere, the solstice takes place during summer, whereas in the southern hemisphere it occurs in winter.

What happens after the longest day of the year?

After the summer solstice, the earth starts to tilt back on itself, decreasing daylight hours, meaning the days become shorter by seconds, and as time goes on, minutes.

How long is the longest day?

In the UK, the longest day begins at 4.43am and ends at 9.21pm, which means that in Britain, we will enjoy 16 hours and 38 minutes of daylight on June 21.

How is the summer solstice celebrated?

For many thousands of years, Stonehenge - England's ancient prehistoric world heritage site - is visited over the summer solstice as a place of worship and celebration.

Individuals, or those in a group, assemble at this ancient site to conduct their own ceremonies or celebrations - the only stipulation of which being that they are respectful and tolerant of others around them.

What is Stonehenge?

No one really knows what the prehistoric monument Stonehenge was actually used for by our ancient ancestors. All we know is that it is thousands of years old - archaeologists have dated it to between 3,000BC and 2,000BC.

Some believe that Stonehenge was an ancient burial ground, and deposits containing human bone from as early as 3,000BC have been found in the ditch.

Whatever its ancient use, Stonehenge now exists as a ring of stones standing seven feet wide and 13 feet high, with each one weighing a mammoth 25 tons. The stones themselves are found within a complex set of Bronze Age and Neolithic earthworks, banks and ditches, among them hundreds of ancient burial mounds.

Unfortunately, whoever left Stonehenge didn't leave any written records, so the true nature of the World Heritage Site will most likely be lost in the mists of time forever.